Polymerization process

ABSTRACT

Process comprising mixing a vinyl chloride polymer latex with vinyl chloride, destroying the latex emulsifying agent which is of the acid salt type, so that the polymer particles pass into the vinyl chloride and polymerizing the latter, preferably under suspension polymerization conditions.

United States Patent 1 Sturt 11] 3,725,375 1 Apr. 3, 1 973 [54]POLYMERIZATION PROCESS [75] Inventor: Alan Charles Sturt, Guildford, En-

gland [73] 'Assignee: BP Chemicals Limited, London, En-

gland [22] Filed: May 14, 1970 211 Appl. No.: 37,334

[30] Foreign Application Priority Data May 19, 1969 Great Britain ..25,418/69 US, Cl. .260/92.8 W, 260/296 CM, 260/878 R, 260/884, 260/885,260/899 [51] Int. Cl. ..C08f3/30, C08f 15/32 [58] Field of Search.260/880, 92.8, 884

[56] I References Cited UNITED STATES PATENTS 3,370,105 2/1968DeBelletaL; ..zso/sso Abe et al. ..260/880 Great Britain ..260/928Primary Examiner-Harry Wong, Jr.

AttorneyLorimer P. Brooks, Alfred L. l-laffner, Jr. I

and Harold Haidt [5 7 ABSTRACT Process comprising mixing a vinylchloride polymer latex with vinyl chloride, destroying the latexemulsifying agent which is of the acid salt type, so that the polymerparticles pass into the vinyl chloride and g polymerizing the latter,preferably under suspension polymerization conditions.

6 Claims, No Drawings POLYMERIZATION PROCESS The present inventionrelates to vinyl chloride polymer compositions and particularly to aprocess for the production of such compositions by polymerizing vinylchloride containing preformed vinyl chloride polymeric material.

It is known that useful vinyl chloride polymer compositions are obtainedby blending one vinyl chloride polymer with another, different vinylchloride polymer, e.g., a suspension polymer with an emulsion polymer.

An object of the present invention is to provide an improved techniquefor the production of such polymer compositions. A further object is toprovide improved vinyl chloride polymer compositions.

According to the present invention the process for the preparation of apolymer composition comprises mixing a vinyl chloride polymer in theform of an aqueous latex stabilized by means of a carboxylic acid saltemulsifying agent with monomeric material consisting essentially ofvinyl chloride, destroying the emulsifying agent without substantiallyaltering the 'size of the vinyl chloride polymer particles, allowingparticles to pass into the monomeric material and polymerizing themonomeric material with said particles dispersed therein.

Any vinyl chloride polymer that can be prepared in the form of anaqueous latex stabilized by means of carboxylic acid salt emulsifyingagent can be used in the process of the present invention. Many suchvinyl chloride polymers are known and mostly they contain more than 50percent by weight and usually more than 75 percent by weight ofpolymerized vinyl chloride. Polyvinyl chloride and copolymers of vinylchloride and up to percent by weight of the copolymerizable materialgive good results.

The vinyl chloride polymer must be in the form of a stable aqueouslatex, i.e., it is distributed throughout a continuous aqueous phase asfinely divided particles which are stabilized and therefore do notcoalesce or settle out because of the presence in theaquous phase of theacid salt emulsifying agent. Such aqueous latices of vinyl chloridepolymers are well known and are usually prepared by the well knownemulsion polymerization technique.

The polymeric material is stabilized by means of a carboxylic acid saltemulsifying agent. The agent has to be destructible, i.e., convertibleto an ineffective form, so that it does not interfere with the operationof the second stage of the process. The emulsifying agents may berepresented by the formula R.COOX where R is a large organic radicalattached to the carboxyl salt group COOX. When a relatively strong acid(HA) i.e., an acid that is stronger than the acid from which theemulsifying agent is obtained, is added to the emulsifying agent thefollowing reaction occurs:

R COOX+HA R.COOH+XA The free acid R.COOH is not an emulsifying agent andthus acidification destroys the carboxylic acid salt type emulsifyingagents. In this system the pH of the system can be reduced gradually andthis gives a controlled hydrolysis of the emulsifier. This ability forgradual diminution of the emulsifying power of the agent is of value inensuring that the size of the polymeric material particles is notsubstantially altered during their present invention.

passage into the monomeric phase according to the process of the presentinvention. It is also possible to destroy such emulsifying agent bydiluting the latex with water which causes hydrolysis of the salt andthe conversion of the emulsifying agent to the non-effective free acidform. The preferred emulsifying agents are water soluble salts ofsaturated fatty acids containing from eight to 20 carbon atoms, e.g.,the alkali metal and ammonium salts of lauric, stearic, palmitic andmyristic acids and mixtures thereof. These preferred emulsifying agentscan be destroyed by adding acid to the system. Alternatively they can bedestroyed by the addition of heavy metal (e.g., calcium, barium, cadmiumand tin) salts to the system. These have the advantage of converting theacid salt emulsifying agents to useful lubricants and stabilizers.Examples of other suitable carboxylic acid salt emulsifying agents arethe rosin acid salts, e.g., alkali metal or ammonium salts ofdisproportionated rosin acids and oleic acid.

The monomeric material consists essentially of vinyl chloride. However,it may contain a minor proportion by weight of other monomers that arecopolymerizable with the vinyl chloride. When the monomeric material isto be polymerized under suspension polymerization conditions it is ofcourse necessary to choose any copolymerizable compound so that themonomeric material can be so polymerized. Generally it is found thatpolymers and copolymers having a glass transition temperature above 20Ccan be formed by suspension sifying agent can be destroyed before themonomeric material is added. Care must be taken when the emulsifyingagent is destroyed to ensure that no coagulation of the vinyl chloridepolymer particles occurs. if this is done the polymer particles passinto the organic phase without substantial change in size. Agglomerationof the particles may occur to form agglomerates in the monomericmaterial. However, in such agglomerates the identity of the individuallatex polymer particles is retained and therefore the process isaccording to the A protective colloid may be present in the system whilethe emulsifying agent is destroyed in order to assist the passage of thevinyl chloride polymer particles into the monomeric phase withoutsubstantial alteration of their size. The protective colloids used inthis way act at the interface of the monomeric material and thepolymeric material and therefore are of the organic type. Examples arepolyvinyl alcohols and cellulose ethers.

The polymerization of the monomeric material may be brought about by anyconvenient means, For example, the monomeric material containing thedispersed particles may be separated from the aqueous phase and thenpolymerized by known mass polymerization techniques. Most suitably,however, the monomeric material is subjected to known suspensionpolymerization procedures in the presence of the aqueous phase of thevinyl chloride polymer latex. The fact that the emulsifying agent isdestroyed means that its concentration in the aqueous phase is lowenough not to give rise to emulsion polymerization and thus there shouldbe no loss of product in the aqueous phase as emulsified material.

The polymerization may be initiated before or after the destruction ofthe emulsifying agent, but it is preferred that the destruction iscompleted before polymerization commences and thus the chance of theformation of unwanted emulsion polymer is reduced.

If the polymerization is to be effected under suspension polymerizationconditions any of the known suspension stabilizer systems for vinylchloride polymerization may be employed. Such suspension stabilizersystems can contain suspending agents of the organic or inorganic typeand can be water soluble or insoluble. Examples of suitable organicsuspending agents are polyvinyl alcohol, partially hydrolyzedpolyvinylacetates, salts of styrenemaleic anhydride copolymers, gelatin,cellulose ethers such as methyl cellulose, hydroxypropyl methylcellulose and hydroxyethyl cellulose. Examples of suitable inorganicsuspending agents are sparingly soluble metal phosphates such as hydroxyapatite. Mixtures of organic and inorganic suspending agents and ofwater soluble and insoluble suspending agents can be used. If thesuspending agent employed is conventional, for example a water solubleorganic agent such as polyvinyl alcohol, it is suitably present in anamount in the range 0005-] .0 percent by weight of the monomericmaterial employed and an inorganic suspending agent such as hydroxyapatite is suitably present in an amount in the range 0.05-l.0 percentby weight of the monomeric material employed.

The suspending agent or the suspension stabilizer system can be addedeither before or after the destruction of the emulsifying agent.

The efficiency of the suspension stabilizer can be increased by the wellknown technique of including buffers and/or wetting agents in thesystem. It is important that the amount of wetting agent should not beso great as to cause emulsification of the monomeric materials. Examplesof suitable wetting agents include anionic surface active agents such assodium caproate and sodium oleate, organic sulphates and sulphonatessuch as long chain alkyl sulphates and sulphonates, alkyl aromaticsulphonates, arylalkyl polyether sulphonates and sodium salts of alkylphosphates.

After the emulsifying agent has been destroyed in the sense that it isno longer present in sufficient quantity to give rise to emulsionpolymerization, there may still be a sufficient quantity of the agentpresent to increase the efficiency of any suspending agent employed inthe final polymerization.

Conventional components of vinyl chloride polymerization systems can bepresent in the polymerization step of the present invention, e.g.,polymerization initiator systems, molecular weight modifiers and thelike. These are chosen according to the requirements of the monomericmaterial being polymerized. Similarly if suspension polymerizationconditions are to be employed conventional phase ratios of organic toaqueous phases can be employed.

It will be readily appreciated that the quantity of vinyl chloridepolymer that can be introduced into the monomeric material is limited bythe need to obtain a polymer in monomer suspension system that can besubsequently polymerized. Generally the polymer originally present inaqueous latex form does not constitute more than 50 percent by weight offinal product.

A particular advantage of the vinyl chloride polymers of the presentinvention is that they possess low fusion times as measured in theBrabender Plasticorder. Moreover they improve the fusion times ofconventional polyvinyl chloride resins when mixed with them over a widerange of proportions. As little as 10 percent by weight can markedlyimprove the fusion time of a conventional resin. It is believed thatthis property is due to the distribution of the carboxylic acid derivedfrom the emulsifying agent on the surfaces of the original latexparticles.

The vinyl chloride polymers of the present invention have goodplasticizer up-take and have a lower fish eye content, lower die-swelland show more rapid banding on a mill than conventional vinyl chloridepolymers.

The following examples illustrate the process of the present invention.The parts by weight (pbw) bear the same relationship to the parts byvolume (pvb) as do grams to milliliters:

Example 1 The following ingredients were employed:

Vinyl chloride 700 pbw Distilled water 2,786 pbw Polyvinyl chloridelatexemulsifying agent, ammonium stearate solids content, 33%

- particle size, 0.05 to 0.3microns 21 pbw polyvinyl alcohol (Elvanol5042) 1.75 pbw Aqueous acetic acid (10% w/w) .l pbv Lauroyl peroxide 2.0pbw The polyvinyl alcohol was dissolved in the distilled water and thelatex was added to the solution. The acetic acid solution was slowlyadded to the stirred solution and the mixture was poured into astainless steel reactor. The lauroyl peroxide was added and the reactorclosed, purged and evacuated. The vinyl chloride was sucked into thereactor. The mixture was stirred at 700 r.p.m. and heated to 60C for 6hours. The mixture was cooled and vented to atmosphere. The product wasfiltered, washed in the filter and dried in a vacuum oven. Microscopicexamination showed that the particle size ranged from to 1,000 a. Theproduct had good plasticizer up-take.

Example 2 The following ingredients were employed:

530 pbw 2,460 pbw particle size, 0.05 to 0.3

510 pbw microns. Polyvinyl alcohol (Elvanol 50-42) 7 pbw Aqueous aceticacid w/w) 23 pbv Lauroyl peroxide 2 pbw The procedure was the same asthat adopted in Example l. Microscopic examination of the dry productindicated the particle sizes lay between 400 and 600 ;1..

Example 3 Vinyl chloride 350 latex-emulsifying Distilled water 2,210 pbwPolyvinyl chloride latexemulsifying agent, ammonium stearate solidscontent, 33%

- particle size, 0.05 to 0.3

microns. 940 pbw Polyvinyl alcohol (Elvanol 5042) 7 pbw Aqueous aceticacid (10% w/w) 40 pbv Lauroyl Peroxide 2 pbw The procedure was the sameas that adopted in Example l. Microscopic examination of the dry productindicated the particle size lay in the region 40 to 200 [1,.

The procedure was the same as that adopted in example 1 except that thepolymerization time was 16 hours. A-granular product was obtained whichhad good plasticizer up-take.

Example 5 The following ingredients were employed:

Vinyl chloride 470 pbw Distilled water 2,580 pbw Polyvinyl chloridelatex emulsifying agent, ammonium stearate solids content 33% particlesize, 0.05 to 0.3 microns- 650 pbw Polyvinyl alcohol (Elvanol 50-42) 7pbw Lauroyl peroxide 2 pbw Aqueous acetic acid (10% w/w) 26 pbv Aqueoussodium hydroxide (10% The polyvinyl alcohol was dissolved in thedistilled water and the sodium hydroxide solution added. The

latex was added and the mixture was poured into a stainless steelreactor. The lauroyl peroxide was added and the reactor closed, purgedwith nitrogen and evacuated. The vinyl chloride was sucked into thereactor and the mixture stirred at 120 rpm. for 40 minutes, during thelast 10 minutes of which, the acetic acid solution was pumped in. Thestirrer speed was increased to 700 rpm. and the mixture heated at 60Cfor 6 hours. The reactor was then cooled and excess vinyl chloridevented to the atmosphere. The product was removed, filtered, washed inthe filter and driedin a vacuum oven at 45C'for 48 hours. Microscopicexamination indicated that the particle size of the dried product laybetween 400 and 800 pt.

Example 6 The following ingredients were employed:

Vinyl chloride 700 pbw Distilled Water 2,576 pbw Polyvinyl chloridelatex emulsifying agent ammonium stearate solids content, 33%

- particle size, 0.05 to 0.3microns. 336 pbw Polyvinyl alcohol (Elvanol50-42) 7 pbw Aqueous sodium hydroxide (10% w/w) 0.4 pbv Aqueous aceticacid (10% w/w) 16 pbv Lauroyl Peroxide 2 pbw The procedure used was thesame as that described in Example 5. Microscopic examination of thedried product indicated that the particle size lay between and 250a.

Example 7 The following ingredients were employed:

Vinyl chloride .700 pbw Distilled water 800 pbw Polyvinyl chloride latexas used in Examples 5 and 6 2,000 pbw Polyvinyl alcohol (Elvanol 5042)21 pbw Aqueous acetic acid 10% w/w) 40 pbv Lauroyl Peroxide 2 pbwAqueous sodium hydroxide 10% The same procedure as described in Example5 was employed except the polymerization time was three hours.Microscopic examination of the dried product indicated that the particlesizes lay in the range 50 to 250 u.

Example 8 The following ingredients were employed:

Vinyl chloride 4.000 51); A polyvinyl chloride latex emulsifying agent,ammonium stearate solids content, 33% by weight. 1 l,000 pbw Distilledwater 5,000 pbw Polyvinyl alcohol (Alcotex 88-10) 70 pbw Aqueous aceticacid (10% w/w) 650 pbv Lauroyl peroxide 10 pbw The polyvinyl alcohol wasdissolved in the water and poured into the reactor. The latex andlauroyl peroxide were added and the reactor was sealed and pressuretested. The reactor was purged and evacuated and the vinyl chloride wassucked in. The mixture was stirred at rpm. for 20 minutes. During thelast 10 minutes, the acetic acid was pumped into the reactor. Thestirrer speed was then increased to 700 rpm. and the charge heated at60C for 10 hours. After cooling the reactor, excess vinyl chloride wasvented off.

The product was separated and washed in a basket centrifuge. It was thendried in an air-circulating overn. Microscopic examination showed thatthe particles were in the range 40200p.. This product and blends ofPercentage of product Fusion Time in blend Minutes 54 35 25 15 12 30 740 4 50 3 70 2.5 100 1 I claim:

1. A process for the preparation of a polymer composition whichcomprises mixing a vinyl chloride polymer in the form of an aqueouslatex stabilized by means of a carboxylic acid salt emulsifying agentwith monomeric material comprising vinyl chloride, and,

either prior to or after said mixing, destroying the emulsifying agentwithout substantially altering the size of the polymeric particles,allowing particles to pass into the monomeric material and polymerizingthe monomeric material with said particles dispersed therein.

2. A process as claimed in claim 1 wherein the emulsifying agent is awater soluble salt of a saturated fatty acid containing from eight to 20carbon atoms.

3. A process as claimed in claim 1, wherein the emulsifying agent isdestroyed by the addition of a relatively strong acid to the system.

4. A process as claimed in claim 1 wherein the vinyl chloride polymer ispolyvinyl chloride or a copolymer of vinyl chloride containing up to 20percent by weight of copolymerizable material.

5. A process as claimed in claim 1, wherein the monomeric materialconsists of vinyl chloride.

6. A process as claimed in claim 1 wherein the monomeric material ispolymerized under suspension polymerization conditions in the presenceof the aqueous phase of the vinyl chloride polymer latex.

2. A process as claimed in claim 1 wherein the emulsifying agent is a water soluble salt of a saturated fatty acid containing from eight to 20 carbon atoms.
 3. A process as claimed in claim 1, wherein the emulsifying agent is destroyed by the addition of a relatively strong acid to the system.
 4. A process as claimed in claim 1 wherein the vinyl chloride polymer is polyvinyl chloride or a copolymer of vinyl chloride containing up to 20 percent by weight of copolymerizable material.
 5. A process as claimed in claim 1, wherein the monomeric material consists of vinyl chloride.
 6. A process as claimed in claim 1 wherein the monomeric material is polymerized under suspension polymerization conditions in the presence of the aqueous phase of the vinyl chloride polymer latex. 